1. Technical Field
This invention relates generally to acoustical reproducing apparatus and, more particularly, to the improved performance of rhomboid shaped speakers.
2. State of the Art
A loudspeaker (or “speaker”) is an electroacoustic transducer that produces sound in response to an electrical audio signal input. The most common form of loudspeaker uses a paper cone supporting a voice coil electromagnet acting on a permanent magnet, but many other types exist. Where accurate reproduction of sound is required, multiple loudspeakers may be used, each reproducing a part of the audible frequency range. Miniature loudspeakers are found in devices such as radio and TV receivers, as well as many forms of music players. Larger loudspeaker systems are used for music, sound reinforcement in theatres and concerts, and in public address systems.
The term “loudspeaker” or “speaker” may refer to individual transducers (known as “drivers”) or to complete speaker systems consisting of an enclosure including one or more drivers. To adequately reproduce a wide range of frequencies, most loudspeaker systems employ more than one driver, particularly for higher sound pressure level or maximum accuracy. Individual drivers are used to reproduce different frequency ranges. The drivers are named subwoofers (for very low frequencies); woofers (low frequencies); mid-range speakers (middle frequencies); tweeters (high frequencies); and sometimes supertweeters, optimized for the highest audible frequencies. The terms for different speaker drivers differ, depending on the application. In two-way systems there is no mid-range driver, so the task of reproducing the mid-range sounds falls upon the woofer and tweeter. Home stereos use the designation “tweeter” for the high frequency driver, while professional concert systems may designate them as “HF” or “highs”. When multiple drivers are used in a system, a “filter network”, called a crossover, separates the incoming signal into different frequency ranges and routes them to the appropriate driver. A loudspeaker system with n separate frequency bands is described as “n-way speakers”: a two-way system will typically have a woofer and a tweeter; a three-way system usually employs a woofer, a mid-range, and a tweeter.
An audio acoustical reproduction apparatus or system typically includes a rectangular housing having at least one speaker and amplifier. The speaker or speaker system converts audio waves into corresponding sound waves. Ideally, a speaker or speaker system should optimize the conversion of audio voltage to density waves of audio frequency and amplitude in a manner that minimizes distortion. The preservation of the fidelity of an audio signal from the pickup to the output in such an apparatus or system is of the utmost importance with respect to the quality of sound generated. In order to achieve maximum fidelity, a number of strategies of been employed including optimization of one or more electromechanical components of the speaker device itself, modifications in the design of the driver or speaker cone; and improvements in the speaker diaphragm, the speaker housing or the resident cavity to which the drivers are coupled. However, both prior and contemporary designs in speakers and speaker systems have not provided the desired audio frequency response.
Acoustical distortion occurs in many ways. One major problem with the frequency response of traditional speakers and speaker systems, for example, results from the high and low frequency drivers being located at different positions within a speaker housing. The frequency response is dependent upon the position of the listener/receiver in relationship to the speaker and, in particular, to these two drivers. The corresponding variation in the time arrival of the entire frequency spectrum, as produced by a combination of high and low frequency drivers that are not concentric, results in degradation of the over frequency response and phase response of the speaker as a function of the placement of the speaker in relation to a listener/receiver.
The trajectory for optimal frequency and phase response emitted by a speaker is also dependent upon the position of the listener/receiver in relation to the speaker or speaker system. As a result, a speaker or speaker housing usually has to be mounted or otherwise positioned at a particular angle with respect to a listener/receiver in order to provide that optimal response trajectory. A typical rectangular housing may, for example, be angled upwards or downwards when a listener (including without limitation a person or animal) or receiver (including without limitation a recording or transmitting device) is located above or below the speaker, respectively. Alternatively, a speaker or housing may be positioned on a surface or suspended at ear level when the trajectory for optimum response requires an inward (e.g. substantially level) directivity. Furthermore, any subsequent change in listener or receiver position, including without limitation when a listener moves from one location in a room to another or from an upright to a supine position, requires a corresponding change in the position of the speaker/housing. Adapting to such changes are often problematic, including without limitation the corresponding adjustments in speaker angle required at an outdoor music venue where a speaker/housing may be mounted high above ground level, and/or the speaker/housing is very large or otherwise difficult to move.
Information relevant to attempts to alleviate such problems by modifying the geometry of the speaker housing or placement/shape of the drivers or other speaker components can be found in the following references: U.S. Pat. Nos. 4,168,762; 4,237,341; 4,440,259; 6,807,284; 7,274,797; 7,570,778; 7,826,633; 7,970,149; 7,997,381; U.S. Patent Appl. No. 2005/0053253; U.S. Patent Appl. No. 2005/0084126; U.S. Patent Appl. No. 2005/0135647; U.S. Patent Appl. No. 2007/0076912; U.S. Patent Appl. No. 2009/0214067; U.S. Patent Appl. No. 2009/0252354; U.S. Patent Appl. No. 2009/0279732; and U.S. Patent Appl. No. 2009/0316947. However, each of these references suffers from one or more of the following disadvantages:
1. The high and low frequency drivers are not concentric, resulting in degradation of the over frequency response and phase response of the speaker as a function of the placement of the speaker in relation to a listener or receiver; and
2. Accurate measurement and labor/time intensive repositioning of a speaker or speaker housing relative to a listener or receiver is required in order to provide that listener or receiver with an adequate or optimal frequency and phase response.
Thus there remains a need within the music industry for speakers and other acoustical apparatus that mitigates or removes the acoustical distortion resulting from driver placement, and which can provide an optimal response to a listener/receiver without requiring accurate measurement or labor/time intensive repositioning.